public static extern bool SetDeviceGammaRamp(IntPtr hDc, ref GammaRamp lpRamp);
public static extern bool GetDeviceGammaRamp(IntPtr hDc, out GammaRamp lpRamp);
public static extern bool SetDeviceGammaRamp(IntPtr hDc, ref GammaRamp lpRamp);
public static extern bool GetDeviceGammaRamp(IntPtr hDc, out GammaRamp lpRamp);